Genetics of the Monoecious Character in Spinach.

HILE spinach (Spina& oleracea L.) is usually considered to be dioecious, W there is a continuous range of monoecious types as regards the proportion of pistillate to staminate flowers per plant. Sex determination in dioecious strains of spinach is controlled by a mechanism that acts as if it were a single factor pair; the pistillate plant is homozygous ( X X ) , and the staminate plant is heterozygous ( X U ) (JANICK and STEVENSON 1954a). The inheritance of the monoecious character has been genetically interpreted by HIRATA and YAMAMOTO (1931), NEGODI (1934), MIRYUTA (1937), LORZ (unpub.), SUGUIMOTO (1948), and BEMIS and WILSON (1953). SUGIMOTO (1948) suggested that a single gene independent of the X Y factors controls monoecism, while BEMIS and WILSON (1953) assume that there are two closely linked factors in addition to the X Y factors. A study of progeny segregation from selected crosses involving pistillate, staminate, and monoecious types was attempted to clarify the genetic mechanisms that bring about the monoecious complex in spinach.